Fiber optic lighting systems are used in a variety of applications to provide a cool, flexible, safe source of light. The assignee of the present invention provides fiber optic light systems for use in signs, displays, swimming pools, landscapes and general area lighting. One such fiber optic light system for providing multi-color light effects is described in U.S. Pat. No. 5,528,714 issued Jun. 18, 1996, to Kingstone et al., assigned to the assignee of the present invention and incorporated by reference herein. A fiber optic lighting system may typically include a light source having a fiber optic cable bundle for transmitting light from the light source to a location remote from the light source. The light source may include an enclosure containing a light bulb, a means for securing the end of a fiber optic cable bundle near the light bulb, a power supply or other electronic equipment, and a fan for providing cooling air to the enclosure.
One of the limiting characteristics of a fiber optic light system is the amount of light that can be delivered from the fiber optic cable. The output of the system depends upon numerous variables, such as the intensity of the light produced by the bulb, the effectiveness of the delivery of the light into the fiber end, and the efficiency of the transmission of the light by the fiber optic cable.
Numerous advances have been made to improve the optical performance of the fiber optic cables themselves. For example, U.S. Pat. No. 5,333,228 issued Jul. 26, 1994, to Kingstone, assigned to the assignee of the present invention and incorporated by reference herein, describes a fiber optic cable having a reflective center core for reflecting inwardly directed emissions back toward the outside surface of the cable.
It is known to increase the amount of light introduced at the inlet end of the fiber optic cable bundle in order to increase the amount of light produced by the system. However, light bulbs used to produce such light, for example incandescent and halogen lamps, produce a significant amount of heat energy along with the visible light energy. As the power of the light bulb is increased, the bulb is placed closer to the ends of the fiber optic cables, and the light is focused onto the fiber ends, it becomes increasingly difficult to provide cooling for the cable ends. It is known that plastic cable fibers will melt at approximately 125 degrees Centigrade. Even local melting of the cable will cause a depression in the cable end, thus causing the cooling air to become stagnant and intensifying the local heating effect. In this manner, even a small local hot spot will quickly destroy the functionality of a cable fiber. Therefore, in order to improve the performance of a fiber optic light source, it is necessary to provide an additional margin of safety against melting of the cable ends. U.S. Pat. No. 5,838,860 issued Nov. 17, 1998, to Kingstone et al., assigned to the assignee of the present invention and incorporated by reference herein, describes the use of a plate of heat absorbing material as part of a temperature control scheme within the enclosure of a fiber optic illumination system. In most designs of fiber optic lighting systems the factor limiting the brightness that can be achieved in the cable is the cooling of the cable ends.
In a light source for a fiber optic system it is necessary to provide both local cooling to the ends of the cable bundle fibers and general cooling for the bulb and other components included in the light source enclosure. The large amount of heat generated by the bulb and other electronics within the enclosure mandates the supply of a high volume of cooling air. However, for cooling the cable end, the volume of air is not as critical as is the velocity of the air, due to the geometry of the cable end and the relatively poor thermal conductivity of the air. In order to provide the required velocity for cooling the fiber end, prior art systems have used fans that are much larger than necessary for the general cooling requirements. As a result, such fans have proven to be noisy and have consumed more electrical power than is necessary for the overall application requirements. Furthermore, prior art fiber optic cable systems incorporating the higher light output of metal halide lamps have been limited. Although these lamps produce more visible light than incandescent and halogen lamps, they also produce more infrared and ultraviolet energy, thereby making it more difficult to provide the necessary cooling to the fiber ends in order to take advantage of these higher output lamps.
Prior art fiber optic light sources generally include an apparatus for positioning a bulb and an associated reflector along an optical axis to direct a beam of light through a lens to the fiber ends. Such an apparatus can be seen in FIG. 2 of the aforementioned U.S. Pat. No. 5,838,860. The reflector design described in that patent is a one piece glass reflector having a generally truncated ellipsoid reflecting portion formed to be integral with a rearward rectangular or rounded base portion. The bulb is typically affixed within the base portion of the reflector with a high temperature adhesive. Therefore, when a bulb fails, it is necessary to replace not only the bulb but also the reflector assembly. The cable ends are held in position by a ferrule assembly that is attached to the light source housing, and the ferrule and reflector are positioned relative to each other by an optical bench.
What is desired is an improved fiber optic lighting system capable of providing a higher level of light intensity. It is an object of this invention to provide an improved fiber optic light source capable of providing high intensity light into the fiber ends without causing damage to the fibers.
It is a further object of this invention to provide such an apparatus with an improved cooling arrangement.
It is a further object of this invention to provide a light source wherein the fiber optic cable can be replaced quickly and without the need for disassembly of the light source housing, while ensuring that the location of the cable ends is held in tight tolerance to a preferred position.
It is a further object of this invention to provide a lower cost apparatus for replacing failed bulbs in a fiber optic light source.
It is a further object of this invention to provide a fiber optic light source that incorporates a metal halide light bulb without the danger of melting of the fiber optic cable bundle ends.
It is yet another object of this invention to provide an efficient and quiet cooling arrangement for a fiber optic cable light source.
These and other objects, features and advantages of the present invention are provided by an improved light source apparatus and methods that are described in greater detail below. The lighting apparatus described herein includes a housing; a wall disposed within the housing and defining a first interior volume and a second interior volume; a lamp assembly disposed within the first interior volume and adapted to produce a beam of light; a fiber optic cable having an input end disposed within the second interior volume and extending through the housing; a lens forming a portion of the wall and positioned to focus the beam of light onto the fiber optic cable input end; a first fan in fluid communication with the first interior volume for moving a first flow of cooling air from exterior of the housing through the first interior volume; and a second fan in fluid communication with the second interior volume and adapted to move a second flow of cooling air from exterior of the housing through the second interior volume across the fiber optic cable input end, the first flow of cooling air and the second flow of cooling air being isolated from each other within the housing.